1. Search the Live music archive for desired stuff (i suggest Club d'elf 2008 03 13)
2. click on the search result you want to download
3. then (ususally)you can download the whole show or click on each individual track and download them separately. choose the MP3 option if your not sure about FLAC files.
unfortunately most Dead soundboards are streaming only but there is still plenty of gems on there!
happy listening let me know if you get stuck